Dane Hartman. Duel for Cannons (1981) (Dirty Harry #1) 173 pp. [pbo]
Publishers description: Dirty Harry Callahan blasts his way from the mean streets of San Francisco to the blazing byways of San Antonio. His target—a crime boss whos got the whole town, including the cops, under his thumb. Harrys all alone now, with nothing but a .44 Magnum and a bagful of dirty tricks between him and instant death!
Setting: San Francisco; San Antonio (Tex.)